If you have a white back drop how do you use gels to tint the back ground. I will be using 4 Alien Bee 800 strobes. A soft box and shoot through umbrella as the main and fill lights, and then also have two 800's with color gels which I would like to try to use to tint the white back round with color. It seems to me that the main and fill will over power the two rear strobes with gels.
Can someone please give me insight on where to start with the settings for this to work.
Thanks!
Using gels with a white BG can be an interesting task depending upon the color and saturation you are looking for. Lighter pastel colors are a little more difficult than darker bolder gels. You also have to be concerned with hotspots as well in some situations. I would set the BG lights with the gels first and do some test exposures until you achieve the color/saturation you are looking for then set the main and fill at whatever settings you need to hold the BG lighting to reach your goal. One thing to watch out for is not to wash out the BG with the main or fill.
Gelling a white background is definitely a challenge. Washing the color out of the background with your foreground lights is always an issue and you're going to have a lot of trouble getting an even color cast, as the color saturation will be directly tied to the amount of light in any place, and thus your light falloff.
This shot was a single head with a pink gel on a white cyc:
Your best bet is keeping your foreground lights as close to your subject as possible and your subject as far away from the background as possible. If you can live with one or more hotspots in the background color it'll be that much easier. If you need an even cast, then I'd think about something like a pair of stripboxes carefully placed so that their light patterns overlap and hide each box's falloff.
With lighting, as in Star Trek, space is the last frontier...
Become acquainted with the inverse-square law, if you are not already. In practical terms it predicts that doubling the distance from a light will decrease its intensity by 1/4, or about 2 stops. So the more space there is between the foreground subject and the background the less the foreground key and fill lights will affect the background. Also the closer the foreground lights are to the subject the more rapidly they will fall-off and the less effect they will have on the background.
If space it limited it may be necessary to make compromises; positioning the foreground lights based on how they affect the background rather than what is the most optimal lighting for what is in the foreground (which will vary, depending on subject and goals for the shot). FWIW, an umbrellas are a poor choice if you want to control the foreground and background independently because they spill light all over in a small space.
As already mentioned starting with a grey background will make it easier to get darker shades with gels.
All things considered colored seamless paper might be an easier approach, especially if you are planning on doing a lot of shot with the same color and want them consistent. Another option is to use the reverse side of seamless flooring which is available in 10' widths and can be painted any color you need...
Yeah, I haven't been very successful in coloring the background. My problem is the main light keep spilling to the background. The following two shots, I asked my son to stand very close to the main light to create a lot of distance from the background.
@seebeyond, your skin tones look decidedly green on the key light side on my calibrated monitor. On the fill side, the background light is spilling on the face
@cwebster: thanks. It might have been due to the post processing. I was playing around with some free lightroom presets. I think the skin tones look Ok on the original. Let me see if I can find the original.
There was a link that showed hwo to do that and other lighting tips on U-Tube some time back but I have lost my links due to having to rebuild my system.
I recall reading that a light gray was better than white for tinting via gels. I was planning on doing that once my order for gels came in from Calumet. Any experience out there with using a gray background? I'll try to dig up my reference.
I know you asked about white background, but I have had much better luck throwing a color on a little darker color paper. I use a roll of 'storm grey' that is pretty close to grey card grey that takes a color much better. The little bit of color it has seems to make it With 2 ab800s against a light grey you should be able to get nice even color. Hit it with un-gelled lights and it can turn rather white too. Like hitting it with a gridded light and it will put a nice gradient
Thanks for all of the responses. I am going to be playing around today with them. Adjusting the bg strobes first is a great idea to try. I have had no luck at all in the past. I am limited in space so I know I am going to have issues off the bat. The hot spots are another big piece of the issue with the space.
I am also going to look into a gray muslin in the future, that may help some too.
Thanks for the ideas everyone, as usual you are all a great help!!!
cgardner wrote:
With lighting, as in Star Trek, space is the last frontier...
Become acquainted with the inverse-square law, if you are not already. In practical terms it predicts that doubling the distance from a light will decrease its intensity by 1/4, or about 2 stops. So the more space there is between the foreground subject and the background the less the foreground key and fill lights will affect the background. Also the closer the foreground lights are to the subject the more rapidly they will fall-off and the less effect they will have on the background.
Close but you got it backwards. It will be reduce to 1/4 not reduced by 1/4
The intensity (or illuminance or irradiance) of light or other linear waves radiating from a point source (energy per unit of area perpendicular to the source) is inversely proportional to the square of the distance from the source; so an object (of the same size) twice as far away, receives only ¼ the energy (in the same time period).
I think that a black background is better for colored gels because the colors are more vibrant and you don't need so much power (less spill on the subject).
Wanted to give an update to my testing. I started off with the white back round. I got really good color when I had just the gel strobes going. The lower the power setting the deeper the color. As I increased the power on the strobes with the gels the color became washed out moving towards white. When I introduced the main and fill lights I was able to get a color tint but no matter what I tried I was losing color depth. I was using a white muslin. I do not have gray muslin so I then tried a black muslin. I must say what a difference. The black muslin acted the complete opposite of the white. At low power the color was there but as I increased the power on the gel strobes the color became much darker. I was actually shocked at how well it worked. I played around with two gels the same color and then mixing colors for a two tone back round and was very happy with the results.
Because I was using a clothe back round you could see the wrinkles. I have a 10ft roll of white paper for back rounds and this left me wishing I had black too. I think I will be picking some up.
With the black clothe you could see dark tint to the color but I think it will look much better with paper.
Overall I must say this has been a great learning experience to me. I would have never thought to try a black back round to increase the color with gels. It also leaves me curious as to how a true gray back round would react.
in any case I again appreciate the help here, thanks again!!
